Measurement input circuit and measurement device

ABSTRACT

A measurement input circuit for a measurement device for measuring an electric signal in a device under test comprises a signal input that receives the electronic signal from the device under test and provides the received electronic signal at a signal node, a direct signal coupling path that is coupled between the signal node an electrical ground and comprises a first impedance value, an alternating signal coupling path that is coupled between the signal node and the electrical ground , and comprises a second impedance value that is lower than the first impedance value, and a signal output that is coupled to the signal node and outputs the received electronic signal.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a Divisional Application of U.S. application Ser.No. 15/632,458, filed on Jun. 26, 2017, which published as U.S.2018/0372779 A1, on Dec. 27, 2018, the disclosures of which areincorporated herein by reference in their entireties.

TECHNICAL FIELD

The present invention relates to a measurement input circuit. Thepresent invention further relates to a measurement device.

BACKGROUND

Although applicable in principal to any system that is used to measureelectric signals, the present invention and its underlying problem willbe hereinafter described in combination with measurement devices likee.g. oscilloscopes.

When measuring electronic signals in a device under test it is importantto take into account the impedance of the device under test as well asof the measurement device.

For example, if the measurement device has a high input impedance, likee.g. 1 MΩ, the source of the test signal (e.g. the device under test)will suffer only a low source loading. Such a high impedance couplingmay be used for high voltages of e.g. up to 300 V. The bandwidth withsuch a high impedance coupling is usually limited to about 500 MHz.

On the other hand, if the measurement device has a low input impedance,like e.g. 50Ω, the source of the test signal (e.g. the device undertest) will suffer a higher source loading. Therefore, the low impedancecoupling may be used for low voltages of e.g. up to 5 V or 12 V. Thebandwidth with such a low impedance coupling may reach up to about 100GHz or more.

Another parameter for performing a signal measurement is the type ofcoupling, i.e. AC coupling or DC coupling. With AC coupling the DCcomponent of the test signal is eliminated e.g. to see low amplituderipples in the signal. With DC coupling the whole signal is transmittedto the measurement device.

Usually, a user will therefore have to select an input impedance for themeasurement device and the type of coupling. Such measurements thereforeoffer little flexibility and multiple measurements have to be performedwith different configurations of the measurement device.

Against this background, the problem addressed by the present inventionis to allow more flexible measurements.

SUMMARY

The present invention solves this object by a measurement input circuitwith the features of claim 1 and by a measurement device with thefeatures of claim 15.

Accordingly it is provided:

-   -   A measurement input circuit for a measurement device for        measuring an electronic signal in a device under test, the        measurement input circuit comprising a signal input, e.g. a test        connector, that receives the electronic signal from the device        under test and provides the received electronic signal at a        signal node, a direct signal coupling path that is coupled        between the signal node and an electrical ground and comprises a        first impedance value, an alternating signal coupling path that        is coupled between the signal node and the electrical ground and        comprises a second impedance value that is lower than the first        impedance value, and a signal output that is coupled to the        signal node and outputs the received electronic signal.

Further, it is provided:

-   -   A measurement device, e.g. an oscilloscope, for measuring an        electronic signal in a device under test, the measurement device        comprising a measurement input circuit, the measurement input        circuit comprising a signal input that receives the electronic        signal from the device under test and provides the received        electronic signal at a signal node, a direct signal coupling        path that is coupled between the signal node and an electrical        ground and comprises a first impedance value, an alternating        signal coupling path that is coupled between the signal node and        the electrical ground, and comprises a second impedance value        that is lower than the first impedance value and a signal output        that is coupled to the signal node and outputs the received        electronic signal.

The present invention is based on the finding that direct signals, likee.g. a DC signal (Direct Current) or a direct voltage signal, can beblocked and that a direct signal coupling path and an alternating signalcoupling path may be provided in parallel.

The present invention therefore provides the measurement input circuit.The measurement input circuit may e.g. be provided as a separate circuiton a substrate and with a dedicated housing. Such a measurement circuitmay e.g. be connected via a connector to a measurement device, like e.g.an oscilloscope. Alternatively, the components of the measurement inputcircuit may be included in a measurement device or may be distributed ina measurement device and a dedicated measurement probe that are coupledby connectors and/or cables.

The signal input may e.g. comprise a connector for connecting the deviceunder test, DUT, to the measurement input circuit. Such a connector maycomprise a metallic or conductive outer shielding and inner contactsthat are covered by the shielding, when the connector is coupled to therespective counterpart. A cable may e.g. be provided that connects the

DUT to the signal input. Such a cable may also comprise a conductiveshielding with inner signal conductors. The electronic signal that hasto be measured is provided to a signal node of the measurement inputcircuit via the signal input.

A direct signal coupling path and an alternating signal coupling pathare provided electrically in parallel between the signal node and anelectrical ground of the measurement input circuit. The direct signalcoupling path or DC signal coupling path may be seen as a low impedanceDC path between the signal node and the electrical ground. Thealternating signal coupling path or AC signal coupling path may be seenas a path for AC signals only, e.g. a signal path that blocks DCsignals.

By providing the direct signal coupling path and the alternating signalcoupling path in parallel, the signals that are usually measuredseparately, i.e. low frequency or DC signals and high frequency signals,will both be present at the signal node.

The signal output is provided to output the electric signals as receivedfrom the DUT and present at the signal node. The signal output may e.g.comprise a connector or the like analogous to the signal input.

The measured electronic signal may then e.g. be further processed byelements of a measurement device that uses the measurement inputcircuit.

Further embodiments of the present invention are subject of the furthersubclaims and of the following description, referring to the drawings.

In a possible embodiment, the direct signal coupling path may comprise afirst resistor with a first resistance between the signal node and theelectrical ground. The first resistance may especially comprise aresistance between 10 kΩ and 100 MΩ, especially a 50 kΩ resistance or a1 MΩ resistance or a 10 MΩ resistance.

Direct signal coupling may be performed with a simple resistor. Such aresistor is a simple electric element with two contacts and a resistiveelement between the two contacts. The relatively high resistance valuesof the first resistor provide a low loading to the source, i.e. the DUT.

In a possible embodiment, the first resistor may comprise a firsttunable resistor. The tunable resistor may be tunable to at least twofirst resistance values. Possible resistance values range between 10 kΩand 100 MΩ, and may e.g. comprise a 50 kΩ resistance or a 1 MΩresistance or a 10 MΩ resistance.

A tunable resistor may e.g. be a potentiometer that may be manuallytuned by a user of the measurement input circuit or the measurementdevice. Alternatively, the tunable resistor may e.g. be anelectronically controllable or digital potentiometer. As furtheralternative, the tunable resistor may also comprise a plurality ofresistors arranged electrically in parallel. Every resistor may beprovided with a switch that allows controllably activating ordeactivating the respective switch. Activating in this respect meansclosing the electrical connection between the signal node and therespective resistor or the respective resistor and ground such thatcurrent may flow through the resistor.

In a possible embodiment, the alternating signal coupling path maycomprise an alternating signal coupling element with a second resistorthat comprises a second resistance in series between the signal node andthe electrical ground. The second resistance may comprises a resistancebetween 10Ω and 100Ω, especially a 50Ω resistance or a 75Ω resistance ora 100 Ω resistance.

The alternating signal coupling path as already indicated above, onlyallows AC signals to pass through. The alternating signal couplingelement may be the element that performs the signal separation of DC andAC signals. The second resistor therefore represents the impedance thatis provided for such AC signals. Usually high frequency signals must bemeasured using a low impedance coupling. The impedance of 10Ω to 100Ωserves the purpose of a low impedance coupling for these signals.

The alternating signal coupling element may e.g. comprise a specificfrequency dependent filter or attenuation property.

The alternating signal coupling element may e.g. comprise a specificcutoff frequency. The cutoff frequency in the case of the alternatingsignal coupling element may be a lower cutoff frequency. The alternatingsignal coupling element may therefore let signals pass through thatcomprise a higher frequency than the cutoff frequency. It is understood,that real high-pass filters, especially of first order, will notcomprise a step-shaped frequency response but a continuous curve-shapedfrequency response.

In a possible embodiment, the alternating signal coupling element maycomprise a capacitor. The capacitor may e.g. comprise a capacitancebetween 1 pF and 100 nF, especially between 1 nF and 10 nF, and moreespecially of 2 nF.

The capacitor may e.g. be a SMD or through-hole element that may be usedin an electric circuit. As an alternative, the capacitor may also beformed on a substrate with traces or conductors, e.g. copper traces on aPCB. In combination with the second resistor, the capacitor forms ahigh-pass filter that only lets signals pass through that have afrequency higher than the cutoff frequency of the high-pass filter.

In a possible embodiment, the capacitor may comprise a tunable capacitorthat is tunable to at least two capacitance values between 1 pF and 100nF. Possible capacitance values are 1 nF, 2 nF and 5 nF.

The tunable capacitor may e.g. comprise a plurality of capacitors withswitches that may be selectively coupled electrically in parallel byclosing the respective switches.

In a possible embodiment, the second resistor may comprise a secondtunable resistor and may be tunable to at least two second resistancevalues. Possible second resistance values range between 10Ω and 100Ω,and may e.g. be 50Ω and 75Ω.

Regarding the second tunable resistor the above said about the firsttunable resistor also applies.

The combination of the tunable capacitor and the tunable second resistorprovide a very flexible alternating signal coupling path that may e.g.be tuned by a user according to the requirements of the respectivemeasurement task.

The tuning of the first resistor, the second resistor and the capacitormay e.g. be performed by a controller of a measurement device. Themeasurement device may comprise a user interface and a user may e.g.select via the user interface a respective measurement mode or settingsfor the first resistor, the second resistor and the capacitor. The userinterface may e.g. comprise a display with a respective GUI. Themeasurement device may further comprise a touch screen or other inputelements, like e.g. a mouse or a keyboard for a user to perform therespective selections.

In a possible embodiment, the measurement input circuit may comprise ameasurement amplifier. An input port of the measurement amplifier may beconnected to the signal node. The measurement amplifier may e.g.comprise an operational amplifier or opamp with further surroundingelectric elements like resistors or the like. Such an operationalamplifier may e.g. comprise one or two signal inputs and an amplifieroutput that provides the amplified signal. Usually the inputs of theoperational amplifier will comprise a high impedance and provide noadditional load to the signal source, e.g. the DUT.

If the input of the measurement amplifier is coupled to signal node, themeasurement amplifier directly receives all signals that are present atthe signal node. The measurement amplifier may therefore directlyamplify all relevant signals.

In a possible embodiment, the measurement amplifier may be a broadbandamplifier with a bandwidth between 1 GHz and 100 GHz, especially 5 GHzor 10 GHz.

In a possible embodiment, the direct signal coupling path may comprisean offset circuit with an offset source and a summing or differentiatingcircuit, e.g. with an operational amplifier. The offset source may be avoltage or current source and may be coupled between the electricalground and the first resistor. An input of the summing ordifferentiating circuit may be coupled between the offset source and thefirst resistor. The summing or differentiating circuit forms the sum ordifference of the electric signal and an output signal of the offsetsource.

The offset circuit may serve to compensate for a DC signal component ofthe electric signal that is measured. The offset circuit may also serveto compensate an offset voltage in the measurement amplifier.

In a possible embodiment, a first input of the measurement amplifier maybe connected to a node between the alternating signal coupling elementand the second resistor. A second input of the measurement amplifier maybe connected to an output of the summing or differentiating circuit.

The measurement amplifier may therefore receive the high frequencysignals via the alternating signal coupling path at its first input. Thesecond input may then be provided with a compensation signal from thesumming or differentiating circuit.

In a possible embodiment, the measurement amplifier may comprise anactive summing or differentiating amplifier. Such an active summing ordifferentiating amplifier may e.g.

comprise an operational amplifier with respective resistors and/orcapacitors.

In a possible embodiment, the output of the summing or differentiatingcircuit may be connected to the node between the alternating signalcoupling element and the second resistor.

The combination of the DC and the AC signals is implicitly performed byproviding the output of the summing or differentiating circuit to thenode between the alternating signal coupling element and the secondresistor. Therefore, the signals may be combined even without using ameasurement amplifier.

In a possible embodiment, the measurement input circuit may comprise amode switch that puts the measurement input circuit in a high impedancemode or a low impedance mode or a hybrid mode.

The mode switch may e.g. comprise a plurality of changeover switchesthat may e.g. serve to activate or bypass the direct signal couplingpath and/or the alternating signal coupling path. A changeover switchmay e.g. couple the signal node either with the input of the directsignal coupling path or ground or leave the connection unconnected.Another changeover switch may e.g. couple the signal node either withthe input of the alternating signal coupling path or ground or leave theconnection open. The switches may e.g. be controlled by a controller ofthe measurement device based on user input.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention andadvantages thereof, reference is now made to the following descriptiontaken in conjunction with the accompanying drawings. The invention isexplained in more detail below using exemplary embodiments which arespecified in the schematic figures of the drawings, in which:

FIG. 1 shows a block diagram of an embodiment of a measurement inputcircuit according to the present invention;

FIG. 2 shows a block diagram of another embodiment of a measurementinput circuit according to the present invention;

FIG. 3 shows a block diagram of an embodiment of a direct signalcoupling path according to the present invention;

FIG. 4 shows a block diagram of an embodiment of an alternating signalcoupling path according to the present invention;

FIG. 5 shows a block diagram of an embodiment of a measurement inputcircuit according to the present invention; and

FIG. 6 shows a block diagram of an embodiment of a measurement deviceaccording to the present invention.

The appended drawings are intended to provide further understanding ofthe embodiments of the invention. They illustrate embodiments and, inconjunction with the description, help to explain principles andconcepts of the invention. Other embodiments and many of the advantagesmentioned become apparent in view of the drawings. The elements in thedrawings are not necessarily shown to scale.

In the drawings, like, functionally equivalent and identically operatingelements, features and components are provided with like reference signsin each case, unless stated other-wise.

DETAILED DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a block diagram of an embodiment of a measurement inputcircuit 100. The measurement input circuit 100 serves to couple a deviceunder test 150 to a measurement device (see e.g. FIG. 6) in order tomeasure an electric signal 101. The measurement input circuit 100performs the input coupling of the device under test 150 and themeasurement device.

The measurement input circuit 100 comprises a signal input 102 that iscoupled to a signal node 103. The signal input 102 may e.g. be aconnector 102. Such a connector 102 may e.g. be coupled to the deviceunder test 150 via a cable, like e.g. a 50Ω cable.

The measurement input circuit 100 further comprises a direct signalcoupling path 104 that is coupled between the signal node 103 and anelectric ground 105. In addition, the measurement input circuit 100comprises an alternating signal coupling path 106 that is coupledbetween the signal node 103 and the electric ground 105. Further, asignal output 107 is coupled to the signal node 103.

The direct signal coupling path 104 and the alternating signal couplingpath 106 both provide different types of couplings. The direct signalcoupling path 104 performs a DC coupling to the device under test 150with a high impedance. The alternating signal coupling path 106 incontrast performs an AC coupling to the device under test 150 with a lowimpedance that is adequate for high frequency signals. At the same timethe alternating signal coupling path 106 may block DC signals. Thismeans that the low impedance of the alternating signal coupling path 106will not be applied to the DC signals. The combination of the directsignal coupling path 104 and the alternating signal coupling path 106therefore provides parallel coupling for DC or low frequency and ACsignals.

At the signal node 103 the signal output 107 therefore acquires the DCor low frequency part and the AC part of the electric signal 101. Theelectric signal 101 may then be measured e.g. with a measurement device.

With the arrangement of the measurement input circuit 100 therefore bothtypes of signals, DC or low frequency and AC signal, may be measured inthe DUT at the same time.

FIG. 2 shows a block diagram of another measurement input circuit 200.The measurement input circuit 200 is based on the measurement inputcircuit 100 and therefore comprises a signal input 202 coupled to asignal node 203. The measurement input circuit 200 further comprises thedirect signal coupling path 204 and the alternating signal coupling path206 and the signal output 207. However, in addition to these elements,the measurement input circuit 200 comprises a measurement amplifier 213.

The measurement amplifier 213 is arranged between the signal node 203and the signal output 207. An input of the measurement amplifier 213 iscoupled to the signal node 203 and an output of the measurementamplifier 213 is coupled to the signal output 207. The measurementamplifier 213 may e.g.

be a high-bandwidth amplifier that may comprise an arrangement ofoperational amplifiers, resistances, capacitors and the like that arecoupled between the input and the output of the measurement amplifier213. The measurement amplifier 213 amplifies the signals present at thesignal node 203. Therefore, the signals may be provided at the signaloutput 207 in an already amplified form for further processing.

In the measurement input circuit 200 the direct signal coupling path 204comprises a resistor 210. The resistor 210 with a first resistance valuedefines the impedance of the direct signal coupling path 204. The firstresistance value of the resistor 210 may be a relatively high resistancevalue of e.g. 10 kΩ to 100 MΩ. The resistor 210 may especially be a 50kΩ resistor or a 1 MΩ resistor or a 10 MΩ resistor. The resistor 210 maybe provided e.g. as a SMD or through hole element with two electricalcontacts.

Further, the alternating signal coupling path 206 comprises analternating signal coupling element 212 with a second resistor 211 inseries. The alternating signal coupling element 212 is embodied as acapacitor. The capacitor will block any DC signal part and only passthrough signals with a frequency that is higher than a lower cutofffrequency of a high pass formed by the capacitor 212 and the resistor211.

The resistor 211 comprises a second resistance value that defines theinput impedance of the measurement input circuit 200 for high frequencysignals. The second resistance value of the resistor 211 may be arelatively low resistance value of e.g. 1Ω to 100Ω. The resistor 211 mayespecially be a 50Ω resistor or a 75Ω resistor. The resistor 211 may beprovided e.g. as a SMD or through hole element with two electricalcontacts.

The capacitor 212 may be a discrete, e.g. SMD or through-hole element.As an alternative the capacitor 212 may also be formed by traces on asubstrate, e.g. by copper traces on a PCB substrate. The capacitancevalue of the capacitor 212 may e.g. be between 1 pF and 100 nF,especially between 1 nF and 10 nF, and more especially of 2 nF.

FIG. 3 shows a block diagram of an embodiment of a direct signalcoupling path 304. The direct signal coupling path 304 is a tunabledirect signal coupling path 304. This means that the resistance value ofthe direct signal coupling path 304 may be tuned to a desired valuewithin certain limits.

The direct signal coupling path 304 comprises a plurality of electricseries arrangements each comprising a resistor 310, 315 and a switch317, 318. The single series arrangements are arranged in parallel in thedirect signal coupling path 304.

This means that the resistors 310, 315 can controllably be connected inparallel between an input node of the direct signal coupling path 304and an output node of the direct signal coupling path 304. It isunderstood, that the two resistors 310, 315 are just exemplarily shownand that any number of resistors with respective switches may beprovided (hinted at by three dots). The resistors 310, 315 may allcomprise the same resistance values. However, it is also possible toprovide the resistors with different resistance values. Differentresistance values may provide for a larger range of possible impedancesof the direct signal coupling path 304.

FIG. 4 shows a block diagram of an embodiment of an alternating signalcoupling path 406. The alternating signal coupling path 406 comprises aparallel arrangement of resistors 411, 420 and a parallel arrangement ofcapacitors 412, 421. Each resistor 411, 420 is arranged in series with adedicated switch 424, 425 and each capacitor 412, 421 is arranged with adedicated switch 422, 423.

As with the direct signal coupling path 304, the alternating signalcoupling path 406 allows controllably connecting the resistors 411, 420in parallel with the switches 411, 420. The same applies to thecapacitors 412, 421 that may also controllably be arranged electricallyin parallel with the switches 422, 423.

The alternating signal coupling path 406 therefore allows controllingthe capacitance value as well as the resistance value of the alternatingsignal coupling path 406. Therefore, the impedance and the cutofffrequency of the alternating signal coupling path 406 may bespecifically modified according to the respective application.

Regarding FIGS. 3 and 4 it is understood that any type of switch 317,318, 417, 418, 422, 423, 424, 425 may be used in the direct signalcoupling path 304 and/or the alternating signal coupling path 406.Possible switches include discrete and manually operated switches, likee.g. DIP switches. Other possible switches include electricallycontrollable switches, like e.g. transistors. Possible transistors maybe bipolar junction transistors, FET transistors or any other type oftransistor.

It is further understood, that one of the resistors and/or thecapacitors may be provided without a switch. This resistors and/orcapacitors will therefore determine the standard impedance andcapacitance of the direct signal coupling path and the alternatingsignal coupling path.

FIG. 5 shows a block diagram of an embodiment of a measurement inputcircuit 500. The measurement input circuit 500 is based on themeasurement input circuit 200. Therefore, the measurement input circuit500 also comprises a signal input 502 coupled to a signal node 503, anda direct signal coupling path 504, an alternating signal coupling path506 and the measurement amplifier 513 coupled to the signal output 507.

In the measurement input circuit 500 the measurement amplifier 513 iscoupled with its first or positive input to the signal node 503. Anegative input of the measurement amplifier 513 is coupled to an outputof the direct signal coupling path 504.

The direct signal coupling path 504 comprises the first resistor 510that is coupled to the signal node 503. On the other end the resistor510 is coupled to a negative input of a differentiating circuit oramplifier 533. The positive input of the differentiating circuit oramplifier 533 is coupled to ground 505. Further, a resistor 530 iscoupled to the negative input of the differentiating circuit oramplifier 533 and an offset source is coupled between the resistor 530and ground 505. Finally, a resistor 531 is coupled between the output ofthe differentiating circuit or amplifier 533 and the negative input ofthe differentiating circuit or amplifier 533. The output of thedifferentiating circuit or amplifier 533 is coupled to the negativeinput of the measurement amplifier 513.

FIG. 6 shows a block diagram of a measurement device 640. Themeasurement device 640 may e.g. be an oscilloscope that comprises ameasurement input circuit 600. The measurement input circuit 600 may beany embodiment of the measurement input circuit 600 as described abovein conjunction with FIGS. 1-5.

The measurement device 640 may be coupled via the measurement inputcircuit 600 and a cable 641 to the device under test 650. As alreadyexplained above, the measurement input circuit 600 allows themeasurement device 640 to measure electric signals within a largefrequency range from DC signals to frequencies of e.g. several GHz. Thisallows measuring signals of devices under test 650 that comprise aplurality of different frequencies. This may e.g. be the case withdevices that may switch between different operating modes. Such devicesmay e.g. transmit control data via a low speed bus, e.g. a 100 kHzcontrol bus, and data via a high speed data transmission, e.g. in theGHz range. Such signals may e.g. be provided by MIPI-Alliance compatibledevices.

The measurement device 640 may comprise user input devices 642, 643 thatmay allow a user to configure the measurement device 640. The user inputdevices 642, 643 may e.g. be used to configure the measurement inputcircuit 600. As indicated above the direct signal coupling path and thealternating signal coupling path of the measurement input circuit 600may be tunable. The user input devices 642, 643 may therefore be used totune the measurement input circuit 600. The user input devices 642, 643may e.g. be used to control the switches as shown in FIGS. 3 and 4. Theuser input devices 642, 643 may therefore be used to set the impedanceof the direct signal coupling path and the impedance and capacitance ofthe alternating signal coupling path of the measurement input circuit.Although not explicitly shown, it is understood that dedicated controllines may be provided between the measurement device 640 and theswitches in the measurement input circuit 600.

The measurement input circuit 600 further comprises a display 644 thatmay be used to display the measured electric signals.

The measurement input circuit 600 is shown as coupled to the measurementdevice 640. However, it is understood that at least some of the elementsof the measurement input circuit 600 may also be distributed in themeasurement device 640.

As an example, the direct signal coupling path may e.g. be provided in aseparate housing and the alternating signal coupling path may beprovided in the measurement device 640. The separate housing may then beconnected to the measurement device 640 e.g. via a dedicated port.

Although not explicitly mentioned, it is understood, that themeasurement device 640 may comprise any other element that is necessaryto perform the function of the measurement device 640. Such devices maye.g. include A/D-converters, D/A-converters, processors, memory devicesand the like.

Although specific embodiments have been illustrated and describedherein, it will be appreciated by those of ordinary skill in the artthat a variety of alternate and/or equivalent implementations exist. Itshould be appreciated that the exemplary embodiment or exemplaryembodiments are only examples, and are not intended to limit the scope,applicability, or configuration in any way. Rather, the foregoingsummary and detailed description will provide those skilled in the artwith a convenient road map for implementing at least one exemplaryembodiment, it being understood that various changes may be made in thefunction and arrangement of elements described in an exemplaryembodiment without departing from the scope as set forth in the appendedclaims and their legal equivalents. Generally, this application isintended to cover any adaptations or variations of the specificembodiments discussed herein.

In the foregoing detailed description, various features are groupedtogether in one or more examples or examples for the purpose ofstreamlining the disclosure. It is understood that the above descriptionis intended to be illustrative, and not restrictive. It is intended tocover all alternatives, modifications and equivalents as may be includedwithin the scope of the invention. Many other examples will be apparentto one skilled in the art upon reviewing the above specification.

Specific nomenclature used in the foregoing specification is used toprovide a thorough understanding of the invention. However, it will beapparent to one skilled in the art in light of the specificationprovided herein that the specific details are not required in order topractice the invention. Thus, the foregoing descriptions of specificembodiments of the present invention are presented for purposes ofillustration and description. They are not intended to be exhaustive orto limit the invention to the precise forms disclosed; obviously manymodifications and variations are possible in view of the aboveteachings. The embodiments were chosen and described in order to bestexplain the principles of the invention and its practical applications,to thereby enable others skilled in the art to best utilize theinvention and various embodiments with various modifications as aresuited to the particular use contemplated. Throughout the specification,the terms “including” and “in which” are used as the plain-Englishequivalents of the respective terms “comprising” and “wherein,”respectively. Moreover, the terms “first,” “second,” and “third,” etc.,are used merely as labels, and are not intended to impose numericalrequirements on or to establish a certain ranking of importance of theirobjects.

LIST OF REFERENCE SIGNS

100, 200, 500, 600 measurement input circuit

101, 201, 501 electric signal

102, 202, 502 signal input

103, 203, 503 signal node

104, 204, 304, 504 direct signal coupling path

105, 205, 305, 405, 505 electrical ground

106, 206, 306, 506 alternating signal coupling path

107, 207, 507 signal output

210, 310, 315, 510 first resistor

211, 411, 420, 511 second resistor

212, 412, 421, 512 capacitor

213, 513 measurement amplifier

317, 318 switch

422, 423, 424, 425 switch

530, 531 resistor

532 offset source

533 differentiating circuit

640 measurement device

641 cable

150, 250, 550, 650 device under test

1. A measurement input circuit for a measurement device for measuring anelectric signal in a device under test, the measurement input circuitcomprising: a user interface that receives a selection of a measurementmode according to requirements of a respective measurement task; asignal input that receives the electronic signal from the device undertest and provides the received electronic signal at a signal node, adirect signal coupling path that is coupled between the signal node andan electrical ground and comprises a first impedance value, analternating signal coupling path that is coupled between the signal nodeand the electrical ground, and comprises a second impedance value thatis lower than the first impedance value, and a signal output that iscoupled to the signal node and outputs the received electronic signal,wherein the direct signal coupling path comprises a first resistor witha first resistance between the signal node and the electrical ground,the first resistor comprises a first tunable resistor and is tunable toat least two first resistance values between 10 kΩ and 100 MΩ; andwherein the alternating signal coupling path comprises an alternatingsignal coupling element with a second resistor with a second resistancein series between the signal node and the electrical ground, and thealternating signal coupling element comprises a tunable capacitor thatis tunable to at least two capacitance values between 1 pF and 100 nF;wherein the measurement input circuit comprises a controller that tunesthe first resistor, the second resistor and the capacitor according to aselected predetermined measurement mode according to requirements of arespective measurement task received from the user interface, whereinthe predetermined measurement mode according to the respectivemeasurement task is selected based on an operating mode of the deviceunder test, wherein the alternating signal coupling path comprises afrequency dependent filter and a cutoff frequency of the alternatingsignal coupling path is set according to the requirements of therespective measurement task.
 2. The measurement input circuit accordingto claim 1, wherein the first resistor is tunable to a 50 kΩ resistanceor a 75 kΩ resistance or a 100 kΩ resistance.
 3. The measurement inputcircuit according to claim 1, wherein the capacitor is tunable to to 1nF and 2 nF and 5 nF.
 4. The measurement input circuit according toclaim 1, wherein the second resistor comprises a second tunable resistorand is tunable to at least two second resistance values between 10Ω and100Ω.
 5. The measurement input circuit according to claim 1, comprisinga measurement amplifier, wherein an input port of the measurementamplifier is connected to the signal node.
 6. The measurement inputcircuit according to claim 5, wherein the measurement amplifier is abroadband amplifier with a bandwidth between 1 GHz and 100 GHz.
 7. Ameasurement device for measuring an electronic signal in a device undertest, the measurement device comprising a measurement input circuit, themeasurement input circuit comprising: a user interface that receives aselection of a measurement mode according to requirements of arespective measurement task; a signal input that receives the electronicsignal from the device under test and provides the received electronicsignal at a signal node, a direct signal coupling path that is coupledbetween the signal node and an electrical ground and comprises a firstimpedance value, an alternating signal coupling path that is coupledbetween the signal node and the electrical ground , and comprises asecond impedance value that is lower than the first impedance value, anda signal output that is coupled to the signal node and outputs thereceived electronic signal, wherein the direct signal coupling pathcomprises a first resistor with a first resistance between the signalnode and the electrical ground, the first resistor comprises a firsttunable resistor and is tunable to at least two first resistance values;and wherein the alternating signal coupling path comprises analternating signal coupling element with a second resistor with a secondresistance in series between the signal node and the electrical ground,and the alternating signal coupling element comprises a tunablecapacitor that is tunable to at least two capacitance values between 1pF and 100 nF; wherein the measurement input circuit comprises acontroller that tunes the first resistor, the second resistor and thecapacitor are set according to the received selection of the measurementmode received from the user interface, and wherein the alternatingsignal coupling path comprises a frequency dependent filter and a cutofffrequency of the alternating signal coupling path is set according tothe requirements of the respective measurement task.
 8. The measurementdevice according to claim 7, wherein the first resistor is tunable toresistance values between 10 kΩ and 100 MΩ.
 9. The measurement deviceaccording to claim 7, wherein the capacitor is tunable to 1 nF and 2 nFand 5 nF.
 10. The measurement device according to claim 7, wherein thesecond resistor comprises a second tunable resistor and is tunable to atleast two first resistance values, especially resistance values between10Ω and 100Ω.
 11. The measurement device according to claim 7,comprising a measurement amplifier, wherein an input port of themeasurement amplifier is connected to the signal node.
 12. Themeasurement device according to claim 11, wherein the measurementamplifier is a broadband amplifier with a bandwidth between 1 GHz and100 GHz.